The present techniques relate to the field of organometallic compositions, olefin polymerization catalyst compositions, and methods for the polymerization and copolymerization of olefins using a catalyst composition.
This section is intended to introduce the reader to aspects of art that may be related to aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
As methods, processes, and equipment within chemical and petrochemical technologies advance, the higher-quality, lower cost materials and products that result become more and more prolific in our everyday lives. In particular, simple molecular building blocks (or monomers) may be brought together into longer chains (or polymers), through a chemical process called polymerization to yield these materials. Polyolefins, a type of polymer widely consumed on an everyday basis, may be produced from various olefin monomers and one or more catalysts. Plastic products from polyolefins are used for retail and pharmaceutical packaging (such as display bags, bottles, and medication containers), food and beverage packaging (such as juice and soda bottles), household and industrial containers (such as pails, drums and boxes), household items (such as appliances, furniture, carpeting, and toys), automobile components, fluid, gas and electrical conduction products (such as cable wrap, pipes, and conduits), and various other industrial and consumer products. The wide variety of residential, commercial and industrial uses for polyolefins has translated into a substantial demand for raw polyolefin which can be extruded, injected, blown or otherwise formed into a final consumable product or component.
Because of this large demand, polyolefin polymers are generally produced using large-scale polymerization reactors, which can produce tons of polyolefin product in short periods of time. In typical polyolefin reaction processes, various components are added to the polymerization reactor, which subjects the components to appropriate conditions to cause the polymerization of monomer to occur. The components can include olefin feed components, diluent components, catalyst system components, and other additives. Upon introducing, for instance, monomer (e.g., ethylene), comonomer (e.g., hexene), and a catalyst system (e.g., a metallocene catalyst) into the polymerization reactor under polymerization conditions, the polymerization reaction process begins to produce a polymer.
Because these polymerization processes are typically performed on a very large scale and, in some instances, on a continuous basis, the reaction conditions within the polymerization reactor may be carefully controlled in an effort to maintain the quality and reproducibility of the polymer product. Indeed, the polymerization reaction conditions and the types of materials used in the polymerization reaction may determine the physical and chemical properties of the polyolefin product, which can be of paramount importance to the polymer product's marketability and ultimate use. However, despite advances within polymerization technologies over the past few decades, consistently obtaining polyolefins with specific properties remains a difficult task, as precise control over polymerization reaction variables is among the more difficult hurdles associated with polyolefin production.
For example, in some circumstances the polymerization conditions may cause a reactor to foul, such as when the polymerized product is formed on the reactor walls or when the product cannot be maintained as a slurry. Fouling may result in a loss in heat transfer, such as due to a reduction in circulation or reduced efficiency at a heat exchanger interface, which may impair or completely negate the capacity to maintain the desired temperature within the reactor. A reactor foul may also result in a reduction in the circulation of the reactor contents and/or in a variation from the desired percent solids (measured by volume or by weight) of the reactor slurry. The weight percent solids (solids wt %) in the reactor may be defined as the ratio of polymer to the total reactor contents. To the extent that a reactor foul may result in deviations from the desired reaction conditions, the polymer product produced during such a reactor foul may not meet the desired specifications; that is, the product may be “off-spec.” In extreme or runaway fouling situations, control of the reaction may be lost entirely, and the reactor may become plugged with polymer, requiring one to three weeks to clear, during which time the reactor may not be operated.